I haven't programmed the VEX yet, but isn't it about the same as programming for the FRC controller?
We used the setPWM command to control the FRC. We have sample code here: "FRC version".
http://www.frcsoft.com/forums/index.php?dlcategory=6
Maybe that will help some, then maybe I need to check out the VEX programming someday I have some time....